don't create notebook_dir if it doesn't exist

IPython/html/notebookapp.py

@@ -521,14 +521,8 b' class NotebookApp(BaseIPythonApplication):'
             # If we receive a non-absolute path, make it absolute.
             self.notebook_dir = os.path.abspath(new)
             return
-        if os.path.exists(new) and not os.path.isdir(new):
-            raise TraitError("notebook dir %r is not a directory" % new)
-        if not os.path.exists(new):
-            self.log.info("Creating notebook dir %s", new)
-            try:
-                os.mkdir(new)
-            except:
-                raise TraitError("Couldn't create notebook dir %r" % new)
+        if not os.path.isdir(new):
+            raise TraitError("No such notebook dir: %r" % new)
         
         # setting App.notebook_dir implies setting notebook and kernel dirs as well
         self.config.FileNotebookManager.notebook_dir = new

IPython/html/tests/test_notebookapp.py

@@ -51,11 +51,12 b' def test_nb_dir():'
         app = NotebookApp(notebook_dir=td)
         nt.assert_equal(app.notebook_dir, td)
 
-def test_create_nb_dir():
+def test_no_create_nb_dir():
     with TemporaryDirectory() as td:
         nbdir = os.path.join(td, 'notebooks')
-        app = NotebookApp(notebook_dir=nbdir)
-        nt.assert_equal(app.notebook_dir, nbdir)
+        app = NotebookApp()
+        with nt.assert_raises(TraitError):
+            app.notebook_dir = nbdir
 
 def test_missing_nb_dir():
     with TemporaryDirectory() as td: